Merge pull request #213 from noritada/fix/scanning-mode-processing

Fix an issue that the 3rd bit of scanning mode in GRIB does not affect processing

Author: jswhit

Changelog

@@ -6,6 +6,7 @@ since version 2.1.4 release
 * allow pygrib.open to take an io.BufferedReader object as an argument
   (issue #83, PR #206)
 * ensure that RuntimeError contains a message of type `str` (PR #212)
+* fix an issue that the 3rd bit of scanning mode does not affect processing (PR #213)
 
 version 2.1.4 (git tag v2.1.4rel)
 ================================

sampledata/scanning_mode.grib2

@@ -1185,12 +1185,7 @@ cdef class gribmessage(object):
                     raise RuntimeError(_get_error_message(err))
                 return longval
             else: # array
-                if self.has_key('jPointsAreConsecutive') and\
-                   self['jPointsAreConsecutive']:
-                    storageorder='F'
-                else:
-                    storageorder='C'
-                datarr = np.zeros(size, int, order=storageorder)
+                datarr = np.zeros(size, int)
                 err = grib_get_long_array(self._gh, name, <long *>datarr.data, &size)
                 if err:
                     raise RuntimeError(_get_error_message(err))
@@ -1205,12 +1200,7 @@ cdef class gribmessage(object):
                     raise RuntimeError(_get_error_message(err))
                 return doubleval
             else: # array
-                if self.has_key('jPointsAreConsecutive') and\
-                   self['jPointsAreConsecutive']:
-                    storageorder='F'
-                else:
-                    storageorder='C'
-                datarr = np.zeros(size, np.double, order=storageorder)
+                datarr = np.zeros(size, np.double)
                 err = grib_get_double_array(self._gh, name, <double *>datarr.data, &size)
                 if err:
                     raise RuntimeError(_get_error_message(err))
@@ -1336,7 +1326,12 @@ cdef class gribmessage(object):
             return datarr
         if ny != GRIB_MISSING_LONG and nx != GRIB_MISSING_LONG and\
            self.expand_reduced:
-            datarr.shape = (ny,nx)
+            if self.has_key('jPointsAreConsecutive') and\
+                self['jPointsAreConsecutive']:
+                storageorder='F'
+            else:
+                storageorder='C'
+            datarr = datarr.reshape(ny, nx, order=storageorder)
         # check scan modes for rect grids.
         if datarr.ndim == 2:
            # columns scan in the -y direction (so flip)

sampledata/scanning_mode_with_bitmap.grib2

@@ -1,5 +1,9 @@
 """Collection of miscellaneous minor tests."""
 
+import os
+from tempfile import NamedTemporaryFile
+
+import numpy as np
 import pygrib
 import pytest
 
@@ -9,3 +13,89 @@ def test_internal_value_type_of_runtime_error():
     with pytest.raises(RuntimeError) as e:
         grbindx.write("nonexistent/path")
     assert type(e.value.args[0]) is str
+
+
+@pytest.mark.parametrize(
+    "data_fname,scanning_mode,expected_values",
+    [
+        (
+            "scanning_mode.grib2",
+            0b00000000,
+            np.array([[0, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode.grib2",
+            0b10000000,
+            np.array([[0, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode.grib2",
+            0b01000000,
+            np.array([[0, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode.grib2",
+            0b00100000,
+            np.array([[0, 3], [1, 4], [2, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode.grib2",
+            0b00010000,
+            np.array([[0, 1], [3, 2], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode.grib2",
+            0b00110000,
+            np.array([[0, 3], [4, 1], [2, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b00000000,
+            np.array([[np.nan, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b10000000,
+            np.array([[np.nan, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b01000000,
+            np.array([[np.nan, 1], [2, 3], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b00100000,
+            np.array([[np.nan, 3], [1, 4], [2, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b00010000,
+            np.array([[np.nan, 1], [3, 2], [4, 5]], dtype=float),
+        ),
+        (
+            "scanning_mode_with_bitmap.grib2",
+            0b00110000,
+            np.array([[np.nan, 3], [4, 1], [2, 5]], dtype=float),
+        ),
+    ],
+)
+def test_scanning_mode(data_fname, scanning_mode, expected_values):
+    template_path = f"../sampledata/{data_fname}"
+    with open(template_path, "rb") as f:
+        template = f.read()
+    scanning_mode_index = 0x6C
+    bytes_ = (
+        template[:scanning_mode_index]
+        + scanning_mode.to_bytes(1, "big")
+        + template[scanning_mode_index + 1 :]
+    )
+    with NamedTemporaryFile(mode="wb", delete=False) as temp:
+        temp.write(bytes_)
+
+    grbs = pygrib.open(temp.name)
+    actual = grbs[1].values
+    np.testing.assert_array_equal(actual, expected_values)
+
+    grbs.close()
+    os.unlink(temp.name)